1. Field of the Invention
The present invention relates to a semiconductor memory device, particularly to a semiconductor memory device that enables high-speed search of data to be searched stored in the semiconductor memory device.
2. Description of the Related Art
A content addressable memory (hereinafter called CAM) is a semiconductor memory device that enables high-speed search by obtaining the address of data generated by comparing stored data with data to be searched, unlike a semiconductor memory device in which stored data is read by addressing.
Examples of CAMs include a structure using a volatile memory device as described in Patent Document 1. In a CAM using a volatile memory device, stored data is lost when the supply of a supply voltage is stopped. Particularly in mobile devices which cannot be easily supplied with the supply voltage stably, the loss of data caused by stopping the supply of the supply voltage causes inconvenience.
In view of the foregoing problem, in recent years, a CAM using a nonvolatile memory device as described in Patent Document 2 has been proposed. Patent Document 2 discloses a CAM in which a nonvolatile memory device formed using a phase change material is used to prevent data from being lost when the supply of a supply voltage is stopped.